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(AMS) at ATLAS Accelerator Mass Spectrometry (AMS) at ATLAS Walter Kutschera Vienna Environmental Research Accelerator (VERA) Fakultät für Physik, Universität Wien, Austria ATLAS 25th Anniversary Celebration Physics Division, Argonne National Laboratory 22-23 October 2010 AMS at ATLAS over the years Year Radioisotope Accelerator Topic 1979 14C, 26Al, 32Si, 36Cl Tandem Detection with split-pole spectrograph 1980 32Si Tandem Half-life measurement (101 yr) 1980 26Al Tandem Cross section 26Mg(p,γ)26Al 1983 44Ti Tandem Half-life measurement (54 yr) 1984 B−−, C−−, O−− Tandem No evidence found ( <10-15) 1984 60Fe Tandem+Linac Half-life measurement (1.5x106 yr) 1984 Free quarks Injector Fermi Lab Cryogenic search for free quarks 1987 41Ca Tandem+Linac+GFM Developing a 41Ca dating method 1993 59Ni Tandem+Linac+FS Solar CR alphas in moon rocks 1994 39Ar, 81Kr ECR+Linac+GFM Developing a detection method 2000 81Kr NSCL (MSU)+FS Groundwater dating 2000 236U ECR+Linac+FMA 236U from 235U (n,γ) 2004 39Ar ECR+Linac+GFM Dating of ocean water (circulation) 2005 63Ni ECR+Linac+GFM Cross section of 62Ni(n,γ)63Ni 2008 39Ar ECR+Linac+GFM Ar with “no“ 39Ar (dark matter search) 2009 146Sm ECR+Linac+GFM Half-life meas. (~108 yr), p-process People from Argonne involved with AMS over the years I. Ahmad, D. Berkovits, P. J. Billquist, F. Borasi, J. Caggiano, P. Collon, C. N. Davids, D. Frekers, B. G. Glagola, J. P. Greene, R. Harkewicz, B. Harss, A. Heinz, D. J. Henderson, W. Henning, C. L. Jiang, W. Kutschera, M. Notani, R. C. Pardo, N. Patel, M. Paul, K. E. Rehm, R. Rejoub, J. P. Schiffer, R. H. Scott, D. Seweryniak, K.W. Shepard, S. Sinha, A. Sozogni, E. J. Stephenson, X, Tang, J. Unsitalo, R. Vondrasek, J. L. Yntema AMS at ATLAS over the years Year Radioisotope Accelerator Topic 1979 14C, 26Al, 32Si, 36Cl Tandem Detection with split-pole spectrograph 1980 32Si Tandem Half-life measurement (101 yr) 1980 26Al Tandem Cross section 26Mg(p,γ)26Al 1983 44Ti Tandem Half-life measurement (54 yr) 1984 B−−, C−−, O−− Tandem No evidence found ( <10-15) 1984 60Fe Tandem+Linac Half-life measurement (1.5x106 yr) 1984 Free quarks Injector Fermi Lab Cryogenic search for free quarks 1987 41Ca Tandem+Linac+GFM Developing a 41Ca dating method 1993 59Ni Tandem+Linac+FS Solar CR alphas in moon rocks 1994 39Ar, 81Kr ECR+Linac+GFM Developing a detection method 2000 81Kr NSCL (MSU)+FS Groundwater dating 2000 236U ECR+Linac+FMA 236U from 235U (n,γ) 2004 39Ar ECR+Linac+GFM Dating of ocean water (circulation) 2005 63Ni ECR+Linac+GFM Cross section of 62Ni(n,γ)63Ni 2008 39Ar ECR+Linac+GFM Ar with “no“ 39Ar (dark matter search) 2009 146Sm ECR+Linac+GFM Half-life meas. (~108 yr), p-process First AMS Paper from Argonne: W. Kutschera, W. Henning, M. Paul, E.J. Stephenson, J. L. Yntema, Radiocarbon 22/3 (1980) 807 … ………………………………... ………………………………… The Concept of Radiocalcium Dating (Drawing: W. Henning) Calcium-41 Concentration in Terrestrial Materials: Prospects for Dating of Pleistocene Samples W. Henning, W. A. Bell, P. J. Billquist, B. G. Glagola, W. Kutschera, Z. Liu, H. F. Lucas, M. Paul, K. E. Rehm, J. L. Yntema, Science 236 (1987) 725 Detection of natural 41Ca/Ca ratio using an enrichment process similar to the first detection of 14C by W. F. Libby 40 years earlier [Phys. Rev. 72 (1947) 931]. Calibration Sample 41Ca/Ca =1.4x10-12 Humo sapiens bone: ~800 BC 41Ca/Ca = 1.2x10-14 W. K. et al., Studies Towards a Method for Radiocalcium of Bones, Radiocarbon 31/3 (1989)311-323 Estimated range of 41Ca/Ca values Overview of 41Ca measurements at Argonne, GSI, Penn, Rehovot W.K. , Nucl. Instr. Meth. B50 (1990) 252-261 A possible solution: Absolute 41Ca dating? 41 41 41 Ca decays by electron capture: Ca + e- → K* + νe 41 41 41 –λ/t Exponential decay of Ca: Cat = Cao x e 41 41 41 The sum of parent and daughter is: Cao = Cat + Kt*(radiogenic) 41 41 41 The age is then independent of Cao:t = 1/λ x ln(1 + Ct/ Kt*) The problem which has to be solved: How to distinguish 41K* from ubiquitus environmental 41K Perhaps this may work: The recoil energy of 41K* after EC due to the emission of νe is only +2.2 eV. In bone, Ca forms apatite crystals: Ca5(PO4)3(OH) A possible solution: Absolute 41Ca dating? 41 41 41 Ca decays by electron capture: Ca + e- → K* + νe 41 41 41 –λ/t Exponential decay of Ca: Cat = Cao x e 41 41 41 The sum of parent and daughter is: Cao = Cat + Kt*(radiogenic) 41 41 41 The age is then independent of Cao:t = 1/λ x ln(1 + Ct/ Kt* ) The problem which has to be solved: How to distinguish 41K* from ubiquitus environmental 41K Perhaps this may work: The recoil energy of 41K* after EC due to the emission of νe is only +2.2 eV. In bone, Ca forms apatite crystals: Ca5(PO4)3(OH) Perhaps 41K* will stay inside the apatite crystals, and can thus be detected after selective chemistry has dissolved everything else of the bone matrix. Measuring the interaction of soft alpha particles from solar cosmic rays with the surface of the moon W.K. et al., Nucl. Instr. Meth. 73 (1993) 403 Apollo 16 flight to the Moon (16-27 April 1972) Lunar Module Orion, with John W. Young working at the Lunar Rover 39 Ar (t1/2 = 269 yr) the ideal tracer to study ocean dynamics Studying the Dynamics of the Oceans with two different cosmogenic radioisotopes Atmosphere 14C: 2% 39Ar: 99% 3000 Surface - Ocean 30 equilibrium time days days Biosphere Ocean 14C: 5% 14C: 93% 39Ar: 1% 14C and 39Ar key data Half-life 14C: 5730 years 39Ar: 269 years Atmospheric isotope ratios 14C/ 14C = 1.2x10-12 39Ar/ 40Ar = 8.1x10-16 Ocean water concentrations 14C: 1.8x109 atoms/litre → 0.4 decays/min 39Ar: 6.5x103 atoms/litre → 17 decays/year Low Level Counting AMS 14 C: 250 litre H2O 0.5 litre H2O 39 Ar: 1500 litre H2O 20 litre H2O ? Production rate of long-lived cosmogenic radionuclides 39Ar detection with ATLAS [P. Collon et al., Nucl. Instr. Meth. B 223-224 (2004) 428] 39 8+ 39 8+ Ar + K 39Ar 39K Ar gas 39Ar8+ + 39K8+ sample 232 MeV Isobar separation of 39Ar(Z=18) from 39K (Z=19) in the gas-filled magnetic spectrograph Dating of deep ocean water with 39 Ar (t1/2 = 269 a) using AMS Sample: SAVE #95 Water depth = 4717 m 39Ar/40Ar = (2.6±0.6)x10-16 = 32% atmospheric Ar “Age“ (decay) = 440 years P. Collon, T.-Z. Lu, W. K. Ann.Rev. Nucl.Part. Sci. 54 (2004) 39-67 Results of 39Ar/40Ar measurements at Argonne __________________________________________________________________________ Sample 39Ar/40Ar Fraction of “Decay age“ (10-16) atm. argon* (years) __________________________________________________________________________ Neutron activated argon 580 ± 40 Atmospheric argon 7.7 ± 0.9 95% South Atlantic Ventilation Experiment #294, water depth = 850 m 5.2 ± 0.7 65% 170 #294, water depth = 5000 m 3.5 ± 0.6 44% 320 #95, water depth = 4717 m 2.6 ± 0.6 32% 440 Great Artesian Basin, Australia, Watson creek well, ground water (0.4 Myr) 0.4 ± 0.2 5% 1200 Atmospheric argon* 8.5 ± 1.2 105% Neutron activated argon 600 ± 40 __________________________________________________________________________ *Normalized to 39Ar/40Ar = 8.1x10-16 = 100%, measured by Low Level Counting (Loosli) Collon et al., Nucl. Instr. Meth. B 223-224 (2004) 428-434 Pushing the detection limit of 39Ar into the realm of interest for dark matter searches with liquid argon Desired (F. Calaprice, Princeton): 39 -3 39 -18 Ar/Ar ~ 10 x ( Ar/Ar)atmosphere ~ 1x10 A lost battle against the isobaric background of 41K The quartz liner of the ECR source One person works – the other watches Sometimes things just don‘t work out The future: 39Ar detectionATTA-IIIwith the Setupmagneto optical trap technique (P. Mueller, Z.-T. Lu et al.) Once you cross the ocean, You are forever on the wrong side. Victor Weisskopf.
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